It may be possible to keep ahead of the ROI curve if you resell the miner for maybe %40-50 of its original price and buy the newest model when it's released.
How often does bitmain release a new s-series? and how much does the resale value drop of the previous generation drop?
How often does bitmain release a new s-series? and how much does the resale value drop of the previous generation drop?
There is no stable timeline. Last year they were releasing new miners every 2-3 months. This year the S7 is the first true new miner, so that's 9 months since last release (S5+ doesn't really count). Pricing is also all over the place. Depends mostly on difficulty, exchange rate etc, i.e. the same things that affect your profitability.
Likely they will have competition from other companies before 9 months. And the other companies likely will have lower NM, even more efficient miner.
But when? We don't know.
well, then if a better and more efficient miner comes along that offer the best bang for my buck, I can just sell my older one and use that money to purchase newer model. So I will probably be paying 50-70% purchase price of the newer model .
This is true in a lot of cases. But cannot guarantee it, just lots of variables.
Also if difficulty keeps going up quick this might not be true on some.
Here in Canada most residential 120V lines supply 15A. Hopefully they'll fix up these instructions before mass-shipping the units out.